Digital communication system which can be utilized as a security system for apartment houses or the like

• US 3,922,664 A
• Filed: 05/28/1974
• Issued: 11/25/1975
• Est. Priority Date: 05/28/1974
• Status: Expired due to Term

• Current Assignee: Carl D. Wadsworth
• Original Assignee: Carl D. Wadsworth
• Inventors: Wadsworth, Carl D.
• Primary Examiner(s): Swann, III, Glen R.
• Application Number:
  US05/473,996
• Time in Patent Office: 546 Days
• Field of Search: 340/31A,280,276,216,288,168S,168R,31R,416,220
• US Class Current: 340/517
• CPC Class Codes: G08B 25/06 using power transmission lines

Abstract

A signal transmitter located in each occupant'"'"''"'"'s apartment of an apartment house, condominium, or the like, is connected to the usual commercial 115 VAC, 60 Hz power line common to all of the apartments including the manager'"'"''"'"'s quarters. A receiver located in the manager'"'"''"'"'s quarters is also connected to the common power line. Each transmitter is designed to superimpose a signal having a predetermined frequency on the 60 Hz frequency of the power line. The signal is initiated when the transmitter is triggered by a commercially available device capable of detecting an invasion of the apartment'"'"''"'"'s security. The length of the signal is predetermined for each apartment to designate the particular apartment which is the source of the signal. The receiver in the manager'"'"''"'"'s quarters is programmed to detect a signal having the predetermined frequency and to provide a corresponding output pulse for every negative-going transition of the 60 Hz line voltage so long as the predetermined signal remains superimposed on the commercial power line. The output of the receiver is connected to commercially available devices which count the pulses and visually display the number of the apartment being threatened. Audible warning devices can also be utilized to alert the manager. The system is also used to monitor and display the reading and operation of numerous other types of installations including service station gas pumps, industrial controls, remote monitoring stations, hospital, motel and school signaling systems.

Claims

1. A digital communication system having at least one transmitting station and at least one receiving station connected by a common power line operating at a given frequency, said transmitting station comprising:

a. a first oscillator capable of producing a wave form having a frequency the same as the power line frequency;

b. first means for synchronizing said first oscillator frequency with the power line frequency;

c. means for generating a predetermined signal frequency;

d. trigger means for initiating the operation of said generating means;

e. means interposed between said trigger means and said generating means and connected to said first oscillator for controlling the initiation of said predetermined signal frequency during the first negative half cycle of said first oscillator after said trigger means has been activated;

f. means connected to said generating means and the common power line for applying said predetermined signal frequency to the common power line;

g. means for counting the number of negative going transitions of said first oscillator after said predetermined signal frequency has been applied to the common power line; and

, h. means connected to said counting means and said generating means for selectively terminating the application of said predetermined signal frequency to the common power line after a predetermined number of negative going transitions of said first oscillator has occurred;

said receiving station comprising;

i. a second oscillator capable of producing a wave form having a frequency the same as the power line frequency;

j. second means for synchronizing said second oscillator frequency with the power line frequency;

k. means for detecting said predetermined signal frequency applied to the common power line;

l. means connected to said frequency detecting means and said second oscillator for producing a single output pulse for every negative going transition of said second oscillator so long as said predetermined signal frequency is detected;

m. means for counting the total number of said output pulses; and

, n. indicia means for relating the total number of said output pulses to the identity of the transmitting station.

2. A digital communication system as in claim 1 in which there is a plurality of transmitting stations;

and in which said predetermined number of negative going transitions of each of said first oscillators differs from the others and is selected so as to distinguish each of said transmitting stations from the others.

3. A digital communication system as in claim 1 in which each of said transmitting and receiving stations includes a standby source of electrical energy;

said energy source being capable of maintaining proper voltages and current levels during any loss of common power line voltages, said energy source maintaining operation of said first and second oscillators and maintaining their frequency and synchronization, said transmitting and receiving stAtions being initially synchronized with respect to the propagation delay time occasioned by the distance separating said stations measured along the common power line.

4. A digital communication system as in claim 1 in which each of said transmitting stations is located in a respective dwelling of a multi-dwelling unit;

in which said receiving station is located at a position remote from said transmitter stations;

in which each dwelling includes means connected to the respective one of said transmitting stations for detecting the invasion of said dwelling; and

a trigger circuit connecting each of said invasion detecting means to the respective one of said transmitting stations to initiate the operation of said transmitting station in the event the respective one of said dwellings in invaded.